I've just become the custodian for an interesting competition road bike from the late forties. It was a custom build for a rider who could only be described as an tech nut extrovert. I'll post more about the whole bike in due course, right now I'm curious about a couple of brackets whose purpose isn't clear to me.

This is the underside of the bottom bracket - is this a braze-on for an Osgear setup?

And, disregarding the Shimano clamp added in the eighties, what on Earth is this here on the chainstay???

RobertFrith wrote:This is the underside of the bottom bracket - is this a braze-on for an Osgear setup?

More pics please! Definitely looks to be a bracket for a tension arm, but an Osgear braze-on should have a slot to retain the spring, example below:

However, a Cyclo Ace has a spring that bears against the outside of the bracket, so this would be a more likely candidate. Also the rudimentary ironmongery on the chainstay could (conceivably) accommodate a modified Ace striking fork. Alternatively, if the gent in question was mechanically minded he might have built his very own Osgear/Cyclo Ace/Simplex style striking fork derailleur. Pictures of the Cyclo Ace below:

I would say it is more for the cyclo 3-4 spd setups,There is a tension spring that would travel along the bottom of chain-stay from the changer to the the clip you have under the BB, similar to my Malvern Star Oppy 37 model.I don't believe it is the Cyclo Ace changer setup, these were similar to the Osgear where an arm attached to the bottom of the down-tube which held the tension while a cable ran from the hand gear lever to the lever which moved back n forth to shift.The image below shows the cyclo 4-speed image of this attached to the changer.That steel plate on the chain-stay looks like a home made job to accommodate the cyclo attachment , the image shows how the changer is mounted, the plate it seems may allow for better and exacting position.I have a few of these cyclo changers with spring so can take a picture if required, ebay always has a few cyclo changers with the long spring, they are common and available.This is only my theory as just when you think you've seen it all something comes along and you get stumped again.

Thanks for the info. It does look as though a 3 speed Cyclo rear changer is the most likely explanation for the bottom bracket fitting. I'd be interested in seeing your pics SL. The ten holed bracket on the RHS chain stay is still a mystery though. Hard to figure out if it's part of the original build or not. The back forks are (were ) chrome plated and these brackets appear to have plating consistent with the rest. There's very little of it left. I'd be interested to know the C to C measurement for a Cyclo RD mount if anyone can run a caliper over one.

The bike is emblazoned with the words "Super Continental". This with Durax cranks and Simplex chainrings as well as brazed on fittings for a Simplex rod changer at the front seem to indicate that the original owner was keen continental gear as opposed to the usual Brit kit. GB stem though...

Close ups of the BB fixture; definitely no slot. Second pic shows a cable guide for the rear derailleur, single cable setup. Could the BB fixture just be a mount for a rear derailleur cable guide? Seems a bit over engineered for that.

RobertFrith wrote:Thanks for the info. It does look as though a 3 speed Cyclo rear changer is the most likely explanation for the bottom bracket fitting. I'd be interested in seeing your pics SL. The ten holed bracket on the RHS chain stay is still a mystery though. Hard to figure out if it's part of the original build or not. The back forks are (were ) chrome plated and these brackets appear to have plating consistent with the rest. There's very little of it left. I'd be interested to know the C to C measurement for a Cyclo RD mount if anyone can run a caliper over one.

The bike is emblazoned with the words "Super Continental". This with Durax cranks and Simplex chainrings as well as brazed on fittings for a Simplex rod changer at the front seem to indicate that the original owner was keen continental gear as opposed to the usual Brit kit. GB stem though...

Close ups of the BB fixture; definitely no slot. Second pic shows a cable guide for the rear derailleur, single cable setup. Could the BB fixture just be a mount for a rear derailleur cable guide? Seems a bit over engineered for that.

Cylco used a twin cable setup for all their derailleurs until the Poly (date?) and Super Olympic of 1948 (?). The Poly, Super Olympic and Benelux were all dropout mounted. Thus a chainstay mount and single-cable guide combined mean a Cyclo is pretty unlikely. Simplex produced a striking fork derailleur like an Osgear. This seems more logical to me than a Cyclo, especially as the mount under the BB looks much more like a tension arm fitting than a spring anchor. Also a spring would tend to foul a cable, which I think is part of the reason Cyclo routed their cables from the top of their chainstay derailleurs. Maybe measure the diameter of the hole in the BB bracket?

I'm pretty sure the fixture under my BB isn't for holding a spring. It's pretty substantial and has definitely had something fitted to it that has worn the paint away in a circle - see the first photo I posted ▲▲.

Here's a Simplex Selection setup I found on flickr (very pretty Gillott), bike is the same age as mine;

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